The problem starts when people do neither: only superficial test suites, not running a few test cases locally, and only start using the debugger when they need help from other people with neither the time nor patience to just stare at the code and argue about things without actually trying to get answers. For example, by provoking the problem and turning on the freaking debugger.

I fear half of my team can't run the application locally. To be honest, there are lots of moving parts in the codebase, but it's not only that.